Blue

When a shifter is born they see everything in black and white. Until they find their soulmate. When they look into each others eyes for the first time that is when they see life in all of its beautiful colors. However the world is a big place not everyone finds their other half. The reason shifters can't see colors is because of an ancient curse put upon them when Fenris the Norse wolf god fell in love with a human thus creating the first shifters when his wife found out she became angry and placed a curse on the creatures. Unbreakable until they find their soul mates.